Iron Phosphate Glass-ceramics

The crystallization of 40Fe2O3-60P2O5, 10ZnO-30Fe2O3-60P2O5 and (43.3−x)PbO–(13.7+x)Fe2O3–43P2O5, (0 < x < 30), glasses and glass-ceramic have been investigated. The structural evolution of glasses during heat treatment at various temperatures and the tendency for crystallization for series of glasses with modified composition are characterized by a dendrite-like phase separation in the early stage of crystallization. Such a behavior leads to the formation of randomly dispersed agglomerates which contain the anhedrally shaped crystallites embedded in glass matrix. Therefore, regardless of the type of crystallization, controlled or spontaneous, the formation of crystalline phases in these phosphate glasses and glass-ceramics is attributed to the disordered interfaces between crystalline grains and glassy matrix

Effect of mixed glass network formers on the electrical transport in alkali germano(boro)phosphate glasses

Učinak miješanih staklotvoraca istraživan je u četiri serije Li2O/Na2O–(B2O3)–P2O5–GeO2 stakala. Sustavnom zamjenom jednog staklotvorca, P2O5, drugim, GeO2 pri čemu udio alkalijskog iona ostaje nepromijenjen, dolazi do promjena u strukturi staklene mreže koje rezultiraju povećanjem električne provodnosti u svim istraživanim serijama stakala. U ternarnim je serijama lokalizirana difuzija pokretljivih Li+ i Na+ iona olakšana kontinuiranim promjenama u fosfatnoj mreži i nastajanjem miješanih germanofosfatnih strukturnih jedinica. S druge strane, u kvaternim serijama, prisutnost B2O3, uzrokuje bržu depolimerizaciju fosfatne mreže i umrežavanje s B4 jedinicama zbog čega su pri niskim udjelima GeO2 vrijednosti DC provodnosti više od odgovarajućih stakala iz ternarne serija. Međutim, pri višim udjelima GeO2 nastaju dodatne miješane jedinice koje utječu na umreženost staklene mreže. Nehomogenosti u staklenoj mreži stvaraju više zamki za Li+ i Na+ ione zbog čega je porast DC provodnosti slabije izražen. Također, litijeve serije pokazuju više vrijednosti DC provodnosti u odnosu na odgovarajuća stakla iz natrijevih serija jer manji ion Li+ može lakše i brže difundirati kroz staklenu mrežu.The mixed glass network former effect was investigated in four series of Li2O/Na2O–(B2O3)– P2O5–GeO2 glasses. Systematic replacement of one glass network former, P2O5, by another, GeO2, while keeping the alkali ion content constant, causes structural modifications of the glass network, resulting in electrical conductivity enhancement for all four glass series. In ternary series, localized diffusion of mobile Li+ and Na+ ions is facilitated by continuous changes in the phosphate network structure and the formation of mixed germanophosphate structural units. On the other hand, in quaternary series, the presence of B2O3 causes depolymerization of the phosphate network and cross-linkages with B4 units, which makes the DC conductivity values higher than those for the corresponding glasses from ternary series at low germanate content. However, at higher GeO2 content, additional mixed units are formed that affect the connectivity of the glass network. The inhomogeneities in the glass network create more traps for Li+ and Na+ ions, which makes the increase in DC conductivity less pronounced. Also, the lithium glasses show higher values of DC conductivity than the corresponding sodium glasses because the smaller Li+ ion can diffuse more easily and faster through the glass network

Investment in hospitality - analysis of Međimurje and Varaždin County

Ovaj rad temelji se na istraživanju investicija u ugostiteljskoj industriji, odnosno u restoraterstvu na području Međimurske i Varaždinske županije. Ugostiteljstvo je gospodarska djelatnost, obuhvaća široko područje hotelijerstva i restoraterstva te zapošljava znatan udio radne snage. Kako je sektor turizma i ugostiteljstva jedan od vodećih djelatnosti u Republici Hrvatskoj, postoji znatan potencijal za razvoj pa tako i za investicije u ugostiteljstvu. Opremanje ugostiteljskog objekta zahtijeva znatna ulaganja u interijer, dizajn te u ostala sredstva potrebna za pružanje kvalitetne usluge. Cilj rada bio je analizirati ugostiteljske objekte na području navedenih županija te utvrditi stanje investicija u toj djelatnosti. Temeljem statističke obrade podataka iz financijskih izvješća dostupnih na stranicama FINE dan je prikaz poslovanja poduzeća, odnosno stanje i kretanje materijalne imovine, dugoročnih obveza i dobiti nakon oporezivanja u vremenskom periodu od pet godina. Prema rezultatima istraživanja u ugostiteljskoj djelatnosti investira se u obje županije, a ivesticije se odnose na izgradnju novih objekata, dogradnju, sanaciju te ulaganje u poboljšanje kvalitete usluge. Obzirom da su kadrovi, uz kvalitetnu uslugu, najvažniji za uspješno poslovanje u ugostiteljstvu, njihovo obrazovanje i edukacija postat će najvažnija i najveća investicija

The attractions of Varazdin as a potential for the development of sustainable tourusm

Ovaj rad temelji se na istraživanju atrakcijske osnove Varaždina kao potencijal za razvoj održivog turizma. Kako je sektor turizma jedna od vodećih djelatnosti u Republici Hrvatskoj, mnogi gradovi baziraju svoj razvoj upravo na razvoju turizma. Turizam je dio svakodnevice, dio sadašnjosti, a time i dio budućnosti cijele planete i upravo je zbog toga održivi razvoj sve češća tema kojom se intenzivno bave sve zemlje i strukture društva. Temeljem toga, planiranje budućeg razvoja gospodarstva, a osobito turizma, nužno je uskladiti s uvažavanjem načela održivog razvoja. Cilj rada je dokazati važnost održivog turizma kao i sposobnost grada Varaždina da svojim atrakcijama privuče posjetitelje. U prvom dijelu rada opisani su novi trendovi u turizmu, eno – gastronomski turizam, održivi turizam kao i utjecaj turizma na okoliš. Također dan je osvrt na turističke atrakcije koje su ključan element turističke destinacije kao i osvrt na destinaciju kao sustav turizma. Nadalje, anketnim upitnikom ispitani su stavovi i mišljenja ispitanika o značaju održivog turizma prilikom odabira turističkog odredišta kao i stupanj atraktivnosti određenih turističkih atrakcija grada Varaždina. Temeljem provedenog istraživanja, odnosno dobivenih rezultata može se zaključiti da većina ispitanika smatra kako održivi turizam može utjecati na atraktivnost i izbor turističke destinacije te kako grad Varaždin ima potencijala za razvoj održivog turizma.This work is based on presenting Varaždin as attraction, based presumption that has potential for devolpment a sustainable tourism. Tourism is in Republic of Croatia leading trade, so many cites base their development on increasing tourism. Tourism is part of every day, part of present and part of future of whole planet, that is why sustainable tourism is concerning all countries and all structures of society. It is necessary to coordinate principles of future development of economy, especially tourism with principles of sustainable tourism. The goal of this paper is to present the importance of sustainable tourism and ability of Varaždin to attract visitors with city attractions. First part is concerning new tren in tourism, enogastronomic tourism, sustainable tourism and impact that tourism has on enviroment. Following it is given a review on touristic attractions that are key element of touristic destination and also review of how destination by it's own is making impact on tourism development. With paper quiz made on random group of people are shown examinee attitude and oppinion on importance of sustainable tourism in choosing a touristic destination and stage of attractiveness some of touristic attractions of Varaždin. According to the results we may conclude that most of respondents think that sustainable tourism can make inpact of attractiveness and selection while choosing a touristic destination and also that city of Varaždin has potential to develop a sustainable tourism

Effect of mixed glass network formers on the electrical transport in alkali germano(boro)phosphate glasses

Učinak miješanih staklotvoraca istraživan je u četiri serije Li2O/Na2O–(B2O3)–P2O5–GeO2 stakala. Sustavnom zamjenom jednog staklotvorca, P2O5, drugim, GeO2 pri čemu udio alkalijskog iona ostaje nepromijenjen, dolazi do promjena u strukturi staklene mreže koje rezultiraju povećanjem električne provodnosti u svim istraživanim serijama stakala. U ternarnim je serijama lokalizirana difuzija pokretljivih Li+ i Na+ iona olakšana kontinuiranim promjenama u fosfatnoj mreži i nastajanjem miješanih germanofosfatnih strukturnih jedinica. S druge strane, u kvaternim serijama, prisutnost B2O3, uzrokuje bržu depolimerizaciju fosfatne mreže i umrežavanje s B4 jedinicama zbog čega su pri niskim udjelima GeO2 vrijednosti DC provodnosti više od odgovarajućih stakala iz ternarne serija. Međutim, pri višim udjelima GeO2 nastaju dodatne miješane jedinice koje utječu na umreženost staklene mreže. Nehomogenosti u staklenoj mreži stvaraju više zamki za Li+ i Na+ ione zbog čega je porast DC provodnosti slabije izražen. Također, litijeve serije pokazuju više vrijednosti DC provodnosti u odnosu na odgovarajuća stakla iz natrijevih serija jer manji ion Li+ može lakše i brže difundirati kroz staklenu mrežu.The mixed glass network former effect was investigated in four series of Li2O/Na2O–(B2O3)– P2O5–GeO2 glasses. Systematic replacement of one glass network former, P2O5, by another, GeO2, while keeping the alkali ion content constant, causes structural modifications of the glass network, resulting in electrical conductivity enhancement for all four glass series. In ternary series, localized diffusion of mobile Li+ and Na+ ions is facilitated by continuous changes in the phosphate network structure and the formation of mixed germanophosphate structural units. On the other hand, in quaternary series, the presence of B2O3 causes depolymerization of the phosphate network and cross-linkages with B4 units, which makes the DC conductivity values higher than those for the corresponding glasses from ternary series at low germanate content. However, at higher GeO2 content, additional mixed units are formed that affect the connectivity of the glass network. The inhomogeneities in the glass network create more traps for Li+ and Na+ ions, which makes the increase in DC conductivity less pronounced. Also, the lithium glasses show higher values of DC conductivity than the corresponding sodium glasses because the smaller Li+ ion can diffuse more easily and faster through the glass network

Effect of mixed glass network formers on the electrical transport in alkali germano(boro)phosphate glasses

Učinak miješanih staklotvoraca istraživan je u četiri serije Li2O/Na2O–(B2O3)–P2O5–GeO2 stakala. Sustavnom zamjenom jednog staklotvorca, P2O5, drugim, GeO2 pri čemu udio alkalijskog iona ostaje nepromijenjen, dolazi do promjena u strukturi staklene mreže koje rezultiraju povećanjem električne provodnosti u svim istraživanim serijama stakala. U ternarnim je serijama lokalizirana difuzija pokretljivih Li+ i Na+ iona olakšana kontinuiranim promjenama u fosfatnoj mreži i nastajanjem miješanih germanofosfatnih strukturnih jedinica. S druge strane, u kvaternim serijama, prisutnost B2O3, uzrokuje bržu depolimerizaciju fosfatne mreže i umrežavanje s B4 jedinicama zbog čega su pri niskim udjelima GeO2 vrijednosti DC provodnosti više od odgovarajućih stakala iz ternarne serija. Međutim, pri višim udjelima GeO2 nastaju dodatne miješane jedinice koje utječu na umreženost staklene mreže. Nehomogenosti u staklenoj mreži stvaraju više zamki za Li+ i Na+ ione zbog čega je porast DC provodnosti slabije izražen. Također, litijeve serije pokazuju više vrijednosti DC provodnosti u odnosu na odgovarajuća stakla iz natrijevih serija jer manji ion Li+ može lakše i brže difundirati kroz staklenu mrežu.The mixed glass network former effect was investigated in four series of Li2O/Na2O–(B2O3)– P2O5–GeO2 glasses. Systematic replacement of one glass network former, P2O5, by another, GeO2, while keeping the alkali ion content constant, causes structural modifications of the glass network, resulting in electrical conductivity enhancement for all four glass series. In ternary series, localized diffusion of mobile Li+ and Na+ ions is facilitated by continuous changes in the phosphate network structure and the formation of mixed germanophosphate structural units. On the other hand, in quaternary series, the presence of B2O3 causes depolymerization of the phosphate network and cross-linkages with B4 units, which makes the DC conductivity values higher than those for the corresponding glasses from ternary series at low germanate content. However, at higher GeO2 content, additional mixed units are formed that affect the connectivity of the glass network. The inhomogeneities in the glass network create more traps for Li+ and Na+ ions, which makes the increase in DC conductivity less pronounced. Also, the lithium glasses show higher values of DC conductivity than the corresponding sodium glasses because the smaller Li+ ion can diffuse more easily and faster through the glass network

Effect of germanium oxide on the structure and properties of lithium borophosphate glasses

International audienc

Insights from local network structures and localized diffusion on the ease of lithium ion transport in two mixed glass-former systems

International audienceThe conductivity enhancement observed in the two glass systems A (40Li2O-(60-x)P2O5-xGeO2) and B (40Li2O-10B2O3-(50-x)P2O5-xGeO2) as the germanate content is increased from 0 to 25 mol % confirms the positive mixed glass-former effect (MGFE) in these systems. In this study, we further employ state-of-the-art NMR techniques along with Raman spectroscopy to probe the local network structures. We use the MIGRATION concept to model the experimental conductivity and permittivity spectra obtained from impedance spectroscopy to understand the scaling features of the spectra and to calculate the value of the spatial extent of the localized diffusion of the lithium ion. As x increases from 0 to 25 mol %, for system A, a continuous increase of the POGe cross-linkages as well as a continuous and strong modification of the phosphate network is observed. In system B, deeper analysis of the 31P magic-angle spinning NMR experiments done using 2D 11B/11B homonuclear and 11B/31P heteronuclear NMR is used to determine the nature of the BOB linkages as well as that of the POB linkages. Modeling of the conductivity spectra shows that the shape parameter of the spectra remains the same for both systems and for all compositions, a feature typical for MGFE. Furthermore, correlating the trends of the spatial extent of localized diffusion with that gleaned from the local structures, we infer that, as the relative germanate content increases, in the ternary glass (system A) the ease of mobility of the Li+ ion is enhanced while in the quaternary glass (system B, x > 0 mol %) it is somewhat hindered

Influence of Nanocrystallization on the Electronic Conductivity of Zinc Iron Phosphate Glass

The effect of nanocrystallization on the electronic conductivity of 10ZnO-30Fe2O3-60P2O5 glass has been investigated using differential thermal analysis (DTA), XRD, Raman, and impedance spectroscopy. the structural evolution of glass during heat treatment at various temperatures for 24 h is characterized by the dendrite-like phase separation in the early stage of nanocrystallization, which produces isolated agglomerates of Fe3(P2O7)2 crystallites. Formation of randomly dispersed agglomerates of Fe3(P2O7)2 crystalline grains results in a decrease of Fe2+-Fe3+ pairs concentration in a predominant glassy phase causing a minimum in electrical conductivity at 8.82 × 10−13 (Ω·cm)−1. with increasing the heating temperature up to the first crystallization temperature, TC1, the conductivity increases and simultaneously the activation energy decreases as the nanocrystallization is more pronounced in these samples. Heat treatment at higher temperature near TC2 exhibits the highest electrical conductivity, 2.97 × 10−10 (Ω·cm)−1. Upon heating at TC2, the sample undergoes further nanocrystallization causing slight decrease in the electrical conductivity. This effect can be understood as a result of the partial blocking of conduction pathways for the polarons along the interfaces between polycrystalline grains and through poorly conductive crystallites. the conductivity of this thermally treated glass is independent of the ZnO content and arises from the polaron hopping between Fe2+ and Fe3+ ions suggesting electronic conduction

Mobilita lithných iontů ve sklech systému B2O3-GeO2-P2O5

Effect of the structural changes, electrical conductivity, and dielectric properties on the addition of a third glass-former, GeO2, to the borophosphate glasses, 40Li2O−10B2O3−(50−x)P2O5−xGeO2, x = 0−25 mol %, has been studied.Byl studován vliv přídavku GeO2, jako třetího sklotvorného oxidu, na strukturu, elektrickou vodivost a dielektrické vlastnosti lithných borofosforečnanových skel, připravených v kompoziční řadě 40Li2O−10B2O3−(50−x)P2O5−xGeO2 (x = 0−25 mol %)